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S T Liu

Publications and source records attributed to S T Liu.

At least 73 records · Page 4Linked to original sources
PubMed1992

Cloning of an Erwinia herbicola gene necessary for gluconic acid production and enhanced mineral phosphate solubilization in Escherichia coli HB101: nucleotide sequence and probable involvement in biosynthesis of the coenzyme pyrroloquinoline quinone.

Escherichia coli is capable of synthesizing the apo-glucose dehydrogenase enzyme (GDH) but not the cofactor pyrroloquinoline quinone (PQQ), which is essential for formation of the holoenzyme. Therefore, in the absence of exogenous PQQ, E. coli does not produce gluconic acid. Evidence is presented to show that the expression of an Erwinia herbicola gene in E. coli HB101(pMCG898) resulted in the production of gluconic acid, which, in turn, implied PQQ biosynthesis. Transposon mutagenesis showed that the essential gene or locus was within a 1.8-kb region of a 4.5-kb insert of the plasmid pMCG898. This 1.8-kb region contained only one apparent open reading frame. In this paper, we present the nucleotide sequence of this open reading frame, a 1,134-bp DNA fragment coding for a protein with an M(r) of 42,160. The deduced sequence of this protein had a high degree of homology with that of gene III (M(r), 43,600) of a PQQ synthase gene complex from Acinetobacter calcoaceticus previously identified by Goosen et al. (J. Bacteriol. 171:447-455, 1989). In minicell analysis, pMCG898 encoded a protein with an M(r) of 41,000. These data indicate that E. coli HB101(pMCG898) produced the GDH-PQQ holoenzyme, which, in turn, catalyzed the oxidation of glucose to gluconic acid in the periplasmic space. As a result of the gluconic acid production, E. coli HB101(pMCG898) showed an enhanced mineral phosphate-solubilizing phenotype due to acid dissolution of the hydroxyapatite substrate.

Acinetobacter calcoaceticus↗
PubMed1992

Cloning and characterization of the latent membrane protein (LMP) of a specific Epstein-Barr virus variant derived from the nasopharyngeal carcinoma in the Taiwanese population.

A DNA fragment containing Epstein-Barr virus (EBV) terminal fragment sequence was obtained from a genomic library of nasopharyngeal carcinoma (NPC). One of the clones (clone 1510) contained the gene encoding latent membrane protein (LMP). Sequence analysis revealed that this gene had 95% homology with the LMP sequence of the B95-8 strain. Among the sequence variations, there was a change from G to T at nucleotide position 169,426, resulting in the loss of an XhoI site in exon 1 of the LMP gene. A pair of primers bracketing the XhoI site were designed to synthesize the EBV DNA fragment from nucleotides 169,081-169,577 by using the polymerase chain reaction (PCR) method. The PCR products were then subject to XhoI digestion and to DNA sequencing analysis. This restriction enzyme site polymorphism along with the sequence variations were also observed in 50 biopsy tissues as well as in the throat washings of 6 out of 20 healthy individuals that we examined, indicating that the EBV strain predominantly existing in these biopsy tissues was different from strains of B95-8, Jijoye or nude mouse passaged cells (C15) with an African origin, but closely resembled other nude mouse passaged CAO cells which were originally derived from China. Balb/c 3T3 cells carrying this NPC-LMP gene showed a transformed cell morphology and were tumorigenic in nude mice. The relationship between this unique type of EBV and NPC has yet to be established.

3T3 Cells↗
PubMed1991

Characterization of the yellow-pigment genes of Erwinia herbicola.

A 6.7 kb DNA fragment containing the pigment genes of Erwinia herbicola Eho13 has been cloned into Escherichia coli. These genes were chromosomally encoded in E. herbicola. The entire DNA fragment could be divided into at least three regions. Deletions in Region I resulted in a non-pigmented phenotype, a deletion in Region II resulted in a pink/yellow phenotype, deletions in Region III resulted in either a pink or a non-pigmented phenotype. Tn1000 insertions in the same regions, however, gave different phenotypes. Insertions in Region II produced a pink phenotype. Insertions in Region III resulted in either a light-yellow or a non-pigmented phenotype. Minicell studies showed that the 6.7 kb DNA fragment encoded at least five proteins (50 kDa, 42 kDa, 36 kDa, 35 kDa and 34 kDa). A 2.7 kb HindIII deletion in Region I caused the disappearance of these proteins, suggesting that this 2.7 kb fragment may play a regulatory role in pigment synthesis. Our results also showed that a 4.1 kb EcoRV fragment consisted of Region I and a part of Region II complemented a pink/yellow clone of Eho10 (pHL545), suggesting that the pigments of Eho13 and Eho10 were probably similar or identical.

Bacterial Proteins↗
PubMed1991

Distribution of type A and type B EBV in patients with nasopharyngeal carcinoma.

The subtypes of Epstein-Barr virus (EBV) according to EBNA 2 genes were investigated in 53 nasopharyngeal carcinoma (NPC) biopsies in Taiwan by polymerase chain reaction (PCR) and by Southern blot hybridization method. EBV DNA was found present in all NPC biopsies. Type A was the predominant type and comprised of 94.3% of the EBV of NPC. Type B or coinfection of type A and type B comprised of only 3.8% and 1.9% respectively.

Adult↗
PubMed1990

High level expression of porcine growth hormone in Escherichia coli from an expression vector containing bacteriophage lambda PL and N gene untranslated region.

An Escherichia coli expression vector, pG408N containing a PL promoter and the upstream untranslated region of the N gene of bacteriophage lambda has been constructed. We have designed a PvuII site immediately behind the untranslated region. A DNA fragment starting with an initiation codon ATG could be inserted into this site for expression. This vector also contains 7 additional cloning sites downstream from the PvuII site. A gene could be cloned into one of these sites and the 5' sequence of this gene could be modified with synthetic oligonucleotides and ligated to the PvuII for the purpose of increasing gene expression. We have also cloned the lambda cl gene into a p15A plasmid. Cotransformation of this plasmid with the expression vector allows the cloning vector pG408N to be used in any E. coli strain. Using this system, we were able to express porcine growth hormone to approximately 35% of total proteins in E. coli DH5 alpha.

Animals↗
PubMed1990

Characterization of two newly established EBV-containing lymphoblastoid cell lines from patients with myeloid leukemias.

Two spontaneous outgrowing Epstein-Barr virus (EBV)-carrying lymphoblastoid cell lines (LCLs), CG2 and CG3, have been established from bone marrow cells of myeloid leukemia patients. CG2 was derived from a patient with chronic myelomonocytic leukemia (CMMoL) and who has a 45 XO karyotype. CG3 was derived from a patient with juvenile chronic myeloid leukemia (CML) and who carries a hypotetraploid karyotype, 91XXYY. Both CG2 and CG3 cells carry the same type of translocation; t(1;19)(q23;p13). Both cell lines are of an early B cell lineage as shown by their reactivities with monoclonal antibodies OKIa, B1, B2 and B4. The combination of horizontal discontinuous agarose slab gel and Southern hybridization results show CG2 and CG3 cells are of monoclonal origin and harbor episomal EBV genomes. Approximately 50 EBV genome equivalents were contained in CG2 and CG3 cells. Immunofluorescence studies demonstrate the expression of EBV-encoded antigen (EBNA) in almost all cells of these two lines. The expression of EA and VCA is only observed in a small percentage of cells and cannot be induced by treatment with TPA and SB. Therefore, CG2 and CG3 cells are probably nonproducer cell lines for EBV. The serum samples from both patients have been shown to contain elevated IgG antibody titers to EBV antigens. Both cells are found to be nontumorigenic in nude mice. These cells may provide an important tool in analyzing molecular epidemiological aspects of EBV infections in diseases such as CMMoL and juvenile CML.

Animals↗
PubMed1990

Detection of Epstein-Barr virus DNA sequences in nasopharyngeal carcinoma cells by enzymatic DNA amplification.

The presence of Epstein-Barr virus (EBV) DNA sequences was examined by the polymerase chain reaction in 50 nasopharyngeal carcinoma (NPC) biopsy specimens and in two primary epithelial tumor cell cultures derived from patients with NPC. The detection limit was a single EBV genome equivalent by agarose gel electrophoresis followed by Southern blot analysis of the amplified products. EBV DNA sequences were detected in all 41 undifferentiated NPC cell specimens, in 2 of 4 moderately differentiated NPC cell specimens, and in 3 of 5 keratinized NPC cell specimens. Undifferentiated NPC cells were also found to contain higher copy numbers of EBV than cells of the other two types of NPC. Our data suggest that EBV replication may be closely associated with the differentiation of NPC tumor cells. The results also demonstrated a sensitive and specific method for the detection of EBV DNA sequences in NPC tumor cells.

Base Sequence↗
PubMed1990

[Clinical Aeromonas hydrophila contain the DNA fragments with nucleotide sequence similar to those of hemolysin and cholera-toxin gene].

The artificially synthesized aquatic Aeromonas hydrophila partial aerolysin gene DNA (Ae, containing 48 oligonucleotides), and partial cholera-toxin gene DNA fragments (C1 and C2, containing 34 and 19 oligonucleotide, respectively) were used as probes to determine their DNA sequence homology to the chromosome DNA of 191 strains of the clinically isolated A. hydrophila, using the colony hybridization test. The three probes had a positive reaction with clinical A. hydrophila strains. Several positive strains of this organism were further screened by cutting reaction with restriction endonuclease BamHI and EcoRI, the alkaline Southern transfer, and DNA hybridization test. Some strains were found to be positive in reacting with Ae and C1, but negative with C2. The findings led to the conclusion that the DNA sequences were homologous among the clinical A. hydrophila toxin gene, cholera-toxin gene and aquatic A. hydrophila aerolysin gene.

Aeromonas↗
PubMed1989

Induction of differentiation in HL-60 cells by retinoic acid and lymphocyte-derived differentiation-inducing factor but not by recombinant G-CSF and GM-CSF.

Various concentrations of retinoic acid (RA, 10(-9) to 10(-7) M), lymphocyte-derived differentiation-inducing factor (DIF, 10-30%), and recombinant human G-CSF (100-4000 U/ml) and GM-CSF (100-4000 U/ml) were used to induce the differentiation of the HL-60 promyelocytic leukemia cells. Retinoic acid at a concentration of 10(-7) M could significantly inhibit the growth of HL-60 cells both in suspension and in soft agar cultures, and induced these cells to differentiate into mature granulocytes capable of reducing nitro-blue tetrazolium and ingesting latex beads. Thirty per cent (v/v) DIF was also an effective inducer of HL-60 cell differentiation, but it triggered the cells to mature into monocytes rather than granulocytes. In contrast, rG-CSF and rGM-CSF had no growth inhibitory effect on HL-60 cells either in suspension or in agar cultures at all concentrations tested, nor could these factors induce HL-60 cells to acquire the more mature granulocytic or monocytic phenotypes. Furthermore, rG-CSF/rGM-CSF had no differentiation-enhancing effect when added to RA-containing HL-60 cultures. These results argue against the efficacy of using CSFs for the treatment of myelocytic leukemia based on the principle of differentiation induction.

Cell Differentiation↗
PubMed1989

[Experimental studies on the significance of processing Eucommia ulmoides Oliv].

The inhibitory action on isolated uterus of middle-pregnancy mice have been compared in Eucommia ulmoides and its salt water processed product. It has been found that after processing the inhibitory action on the automatic contraction of isolated uterus, the antagonism on spasmodis contraction caused by acetylcholine are increased, but the antagonism on spasmodis contraction caused by pituitarium posterius and the Pb content are decreased.

Animals↗
PubMed1986

Cloning and regulation of Erwinia herbicola pigment genes.

The genes coding for yellow pigment production in Erwinia herbicola Eho10 (ATCC 39368) were cloned and localized to a 12.4-kilobase (kb) chromosomal fragment. A 2.3-kb AvaI deletion in the cloned fragment resulted in the production of a pink-yellow pigment, a possible precursor of the yellow pigment. Production of yellow pigment in both E. herbicola Eho10 and pigmented Escherichia coli clones was inhibited by glucose. When the pigment genes were transformed into a cya (adenylate cyclase) E. coli mutant, no expression was observed unless exogenous cyclic AMP was provided, which suggests that cyclic AMP is involved in the regulation of pigment gene expression. In E. coli minicells, the 12.4-kb fragment specified the synthesis of at least seven polypeptides. The 2.3-kb AvaI deletion resulted in the loss of a 37K polypeptide and the appearance of a polypeptide of 40 kilodaltons (40K polypeptide). The synthesis of the 37K polypeptide, which appears to be required for yellow pigment production, was not repressed by the presence of glucose in the culture medium, as was the synthesis of other polypeptides specified by the 12.4-kb fragment, suggesting that there are at least two types of gene regulation involved in yellow pigment synthesis. DNA hybridization studies indicated that different yellow pigment genes exist among different E. herbicola strains. None of six pigmented plant pathogenic bacteria examined, Agrobacterium tumefaciens C58, Cornyebacterium flaccumfaciens 1D2, Erwinia rubrifaciens 6D364, Pseudomonas syringae ATCC 19310, Xanthomonas campestris 25D11, and "Xanthomonas oryzae" 17D54, exhibited homology with the cloned pigment genes.

Cloning, Molecular↗
PubMed1982

The influence of polyphosphate ions on the precipitation of calcium oxalate.

We studied the growth of calcium oxalate monohydrate (COM) crystals in stirred suspensions by following the changes in ionic conductivity of supersaturated solutions at 25 +/- 0.02C. At a pH of 6.9-7.2, in the presence of polyphosphate ion, crystallization proceeded by an initial rapid step followed by a markedly reduced growth rate as compared with that in pure supersaturated solution. The initial surge was reduced as the polyphosphate concentration reached 1.6 X 10(-6) M, which can be interpreted as evidence of either surface nucleation or the incomplete adsorption of inhibitor at the active growth sites. In spontaneous precipitation experiments made in the presence of polyphosphate ions, the formation of calcium oxalate dihydrate and trihydrate is favored together with appreciable coprecipitation of additive ions.

Adsorption↗
PubMed1982

Agrobacterium Ti plasmid indoleacetic acid gene is required for crown gall oncogenesis.

A gene (iaaP) necessary for virulence and indoleacetic acid (IAA) production has been located on a nopaline Ti plasmid of Agrobacterium tumefaciens C58. iaaP function was established by using transformation to insert nopaline or octopine Ti plasmids into an avirulent, Ti plasmid-free mutant 1D1293-3 that was defective in IAA synthesis (iaaC(-)). The resulting transformants produced increased levels of IAA and virulence was restored. When these transformants were cured of their Ti plasmid, virulence and high IAA production levels were concomitantly lost. A Tn5 mutagenized TiC58 plasmid, deficient in the ability to direct increased synthesis of IAA, was inserted by transformation into mutant 1D1293-3. The resulting transformants 1D1293-3 (TiC58::Tn5) remained avirulent and iaaP(-). Restriction analysis of the TiC58::Tn5 plasmid DNA identified the iaaP gene at 20.9 kilobases to the left of the T-DNA. A major aromatic-amino-acid aminotransferase is coded by the iaaC gene, but not by the iaaP gene. The possible reasons for the iaaP locus to be situated outside the T-DNA region are discussed.

Journal Article↗